I looked at last years power consumption according to my utility company and found something strange. I have 3 phase power coming into the house, but all the loads are single phase so outlets are distributed between the phases. Late in 2023 I had a solar system installed with a 3 phase Huawei sun2000 inverter, which comes with a smart meter and an app.
Export to grid is disabled (paperwork's taking forever), and the app's graphs confirm we're only producing power when a load is on. The problem:
Utility meter reports that we consumed 3700 kwh last year, but the inverter app reports 4250 kwh, out of which 2650 kwh coming from the grid, the rest (38%) from PV. The 1000 kwh difference is significant for me, because of a tiered system it cost us ~500 euros last year, and I'm trying to understand where the issue is. Can the inverter's own metering be this much off?
The main thing i don't understand is how the 3 phase inverter works with a large, single-phase load, let's say a dryer. For instance, if my dryer is on phase A and consumes 3 kw when running, the solar array can only produce 3 kw, but isn't that balanced over the 3 phases? Does that mean I'm generating 1 kw on phase A, exporting 2 kw to the grid on phases B and C and importing the 2 kw back on A? My understanding is that the inverter must balance the 3 phases.
Interestingly, if I run this calculation on the year's reports, the numbers do line up: 1600 (generated from PV) * 2/3 + 2650 (imported from grid) = 3716, which is pretty much what the utility company measured.
